1. Field of the Invention
The present invention relates to a vertical cavity surface emitting laser element that comprises: a first multilayer film on a lower side of the vertical cavity surface emitting laser element and a second multilayer film on an upper side of the vertical cavity surface emitting laser. The first multilayer film includes a first reflecting mirror that is formed by exploiting a difference in index of refraction between a first layer of the first multilayer film and a second layer of the first multilayer film. The second multi-layer film includes a second reflecting mirror, which is formed by exploiting a difference in index of refraction between a first layer of the second multilayer film and a second layer of the second multilayer film.
2. Description of the Related Art
A surface emitting laser element of a vertical cavity type (VC-SEL: referred to as a surface emitting laser element hereinafter) can be utilized as a light source (e.g., an optical interconnection) in optical communication applications. Please refer to Japanese Patent Application Publication No. 2005-252111 (Patent Document 1 ) for further applications of surface emitting lasers. A surface emitting laser element can emit laser light in a direction vertical to a substrate of the surface emitting laser element. Due to this property, the surface emitting laser element can be arrayed with other surface emitting laser elements on the same substrate. Advantages of such surface emitting laser elements include, for example, the ability to perform a laser oscillation with a lower threshold electrical current a lower power consumption as lower compared to other conventional laser elements due to a smaller volume of an active layer of surface emitting laser elements compared to other conventional laser elements. Furthermore, in connection with the surface emitting laser element, a distributed Bragg reflector (DBR) mirror can be utilized to configure a resonator in accordance with the surface emitting laser element.
When a DBR mirror is accumulated onto a substrate, dislocations occur due to a lattice mismatch between the substrate and the DBR mirror, and hence, a reliability of the surface emitting laser element is decreased. Previously, it has been proposed that in order to decrease the dislocation, a surface emitting laser element can include a substrate with added indium (In) and decreased a curvature (refer to Patent Document 1), or a surface emitting laser element with added nitrogen, which maintains a lattice match between the substrate and the DBR mirror (refer to Japanese Patent Application Publication No. H10 (1998) 173295 (hereinafter Patent Document 2) and Japanese Patent Application Publication No. H06 (1994) 037355 (hereinafter Patent Document 3), or the like.
However, a problem with the surface emitting laser element in accordance with Patent Document 1 is that it is difficult to add the surface emitting laser element uniformly as it into the substrate. Moreover, Patent Document 1 does not mentioned a specific amount of nitrogen that enables the surface emitting laser element to decrease occurrences of dislocation. Although both Patent Document 2 and Patent Document 3 mention an addition of nitrogen into a material of a semiconductor that is designed to configure a DBR mirror, each exhibits a problem that it is difficult to produce a surface emitting laser element in which any occurrence of dislocation can be suppressed.
And, therefore, an object in accordance with the present invention is to provide a more reliable vertical cavity surface emitting laser element that is designed to suppress any occurrences of dislocation, even when the vertical cavity surface emitting laser element includes a DBR mirror formed on a substrate.